Clive740
Tony Robbins and Bruce Lee say that one shouldn't talk about oneself like that. Especially since you did such an impressive job on that Volvo already. Honest self-criticism's okay though IMO, I have plenty of that myself. 🙂
I posted that diagram, because I thought in my late Friday night daze that the current for the brake lights was going through the electronic circuit/transistor in the middle, but it isn't (it's going straight from pin 9 to pin 10 and 11), nevertheless I decided to leave the diagram.
I was going to post suggestions on how to work out the polarity at the tail light assembly, but ultimately if the polarity had been incorrect, then you would have had to get another LED bulb anyway.
There's a solution that does away with the polarity of the LEDs, which is to get polarity agnostic/universal polarity LEDs, there's more than 1 brand of those types available. For convenience though I suggest you search for a store that stocks the "STEDI" brand (such as Repco?), because they seem easier to find in Australia:
https://www.stedi.com.au/2-pack-bay15d-1157-p21-5w-ba15d-20smd-3030-led.html
(Edit: They have lots of stockists, ask them if you can return the bulbs if they don't work because $40 isn't all that cheap https://www.stedi.com.au/stockists/ )
KEY TECHNICAL FEATURES | BAY15D
CANBUS friendly - resistive Canbus cancellation built-in
Not Polarity Sensitive - our BA15D won't fail if you plug them in the wrong way.
Constant Current circuit - Avoids compromising LED life & provides consistent illumination across all LEDs
Compatible from 9v to 30v circuits.
20 SMD LED for uniform light distribution
BAY15D also replace1016 / 1034 / 1076 / 1130 / 1154 / 1157 / 1158 / 1493 / 2057 / 2357 / 2397 / 3496 / 7225 / 7528 / P21/5W
COMMON USES FOR BA15D GLOBES
Tail Lights
Parker Lights
Brake Lights
Sold in packs of 2
